Let CancelableRequest Execute callbacks which do delete this.
Let CancelableRequest Execute callbacks which do delete this.

By checking canceled() again before calling NotifyCompleted, we avoid
assumptions that we're not canceled from the callback.  This solves 2 issues:
1) The NOTREACHED in the provider which tries to remove the pending_request.
2) Trying to call DidExecute on a deleted consumer_.

BUG=77777, 82156
R=sky@chromium.org
TEST=python chrome/test/functional/imports.py imports.ImportsTest.testImportFirefoxDataTwice

Review URL: http://codereview.chromium.org/7001015

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@84889 0039d316-1c4b-4281-b951-d872f2087c98

jaruba/chromium.src,timopulkkinen/BubbleFish,hujiajie/pa-chromium,junmin-zhu/chromium-rivertrail,Fireblend/chromium-crosswalk,pozdnyakov/chromium-crosswalk,hujiajie/pa-chromium,fujunwei/chromium-crosswalk,dednal/chromium.src,hgl888/chromium-crosswalk,krieger-od/nwjs_chromium.src,Pluto-tv/chromium-crosswalk,rogerwang/chromium,Pluto-tv/chromium-crosswalk,markYoungH/chromium.src,junmin-zhu/chromium-rivertrail,junmin-zhu/chromium-rivertrail,Jonekee/chromium.src,chuan9/chromium-crosswalk,hujiajie/pa-chromium,mohamed--abdel-maksoud/chromium.src,crosswalk-project/chromium-crosswalk-efl,anirudhSK/chromium,nacl-webkit/chrome_deps,mohamed--abdel-maksoud/chromium.src,zcbenz/cefode-chromium,markYoungH/chromium.src,dushu1203/chromium.src,rogerwang/chromium,markYoungH/chromium.src,pozdnyakov/chromium-crosswalk,pozdnyakov/chromium-crosswalk,ChromiumWebApps/chromium,Fireblend/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Jonekee/chromium.src,hgl888/chromium-crosswalk-efl,keishi/chromium,TheTypoMaster/chromium-crosswalk,axinging/chromium-crosswalk,Fireblend/chromium-crosswalk,ChromiumWebApps/chromium,patrickm/chromium.src,patrickm/chromium.src,M4sse/chromium.src,fujunwei/chromium-crosswalk,Chilledheart/chromium,keishi/chromium,ChromiumWebApps/chromium,markYoungH/chromium.src,Pluto-tv/chromium-crosswalk,Chilledheart/chromium,TheTypoMaster/chromium-crosswalk,ChromiumWebApps/chromium,mohamed--abdel-maksoud/chromium.src,robclark/chromium,littlstar/chromium.src,junmin-zhu/chromium-rivertrail,dushu1203/chromium.src,mogoweb/chromium-crosswalk,robclark/chromium,jaruba/chromium.src,Chilledheart/chromium,markYoungH/chromium.src,mogoweb/chromium-crosswalk,Chilledheart/chromium,mohamed--abdel-maksoud/chromium.src,littlstar/chromium.src,markYoungH/chromium.src,rogerwang/chromium,rogerwang/chromium,robclark/chromium,littlstar/chromium.src,Chilledheart/chromium,M4sse/chromium.src,Just-D/chromium-1,ltilve/chromium,Fireblend/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,krieger-od/nwjs_chromium.src,anirudhSK/chromium,fujunwei/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,zcbenz/cefode-chromium,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,hujiajie/pa-chromium,dushu1203/chromium.src,krieger-od/nwjs_chromium.src,nacl-webkit/chrome_deps,jaruba/chromium.src,fujunwei/chromium-crosswalk,ondra-novak/chromium.src,pozdnyakov/chromium-crosswalk,hgl888/chromium-crosswalk-efl,jaruba/chromium.src,zcbenz/cefode-chromium,Jonekee/chromium.src,fujunwei/chromium-crosswalk,zcbenz/cefode-chromium,ltilve/chromium,anirudhSK/chromium,ChromiumWebApps/chromium,zcbenz/cefode-chromium,M4sse/chromium.src,robclark/chromium,robclark/chromium,dushu1203/chromium.src,mogoweb/chromium-crosswalk,timopulkkinen/BubbleFish,Just-D/chromium-1,krieger-od/nwjs_chromium.src,chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,dushu1203/chromium.src,ChromiumWebApps/chromium,PeterWangIntel/chromium-crosswalk,Just-D/chromium-1,mogoweb/chromium-crosswalk,bright-sparks/chromium-spacewalk,crosswalk-project/chromium-crosswalk-efl,ondra-novak/chromium.src,M4sse/chromium.src,mogoweb/chromium-crosswalk,jaruba/chromium.src,M4sse/chromium.src,timopulkkinen/BubbleFish,zcbenz/cefode-chromium,nacl-webkit/chrome_deps,rogerwang/chromium,nacl-webkit/chrome_deps,littlstar/chromium.src,axinging/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,pozdnyakov/chromium-crosswalk,hujiajie/pa-chromium,Fireblend/chromium-crosswalk,littlstar/chromium.src,dushu1203/chromium.src,Jonekee/chromium.src,bright-sparks/chromium-spacewalk,patrickm/chromium.src,pozdnyakov/chromium-crosswalk,Jonekee/chromium.src,mogoweb/chromium-crosswalk,ondra-novak/chromium.src,ondra-novak/chromium.src,fujunwei/chromium-crosswalk,hgl888/chromium-crosswalk,markYoungH/chromium.src,ChromiumWebApps/chromium,Pluto-tv/chromium-crosswalk,hujiajie/pa-chromium,nacl-webkit/chrome_deps,dednal/chromium.src,Pluto-tv/chromium-crosswalk,ltilve/chromium,Fireblend/chromium-crosswalk,dednal/chromium.src,ltilve/chromium,ltilve/chromium,nacl-webkit/chrome_deps,chuan9/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,Pluto-tv/chromium-crosswalk,ChromiumWebApps/chromium,ondra-novak/chromium.src,Just-D/chromium-1,Jonekee/chromium.src,mogoweb/chromium-crosswalk,hgl888/chromium-crosswalk-efl,nacl-webkit/chrome_deps,chuan9/chromium-crosswalk,M4sse/chromium.src,crosswalk-project/chromium-crosswalk-efl,junmin-zhu/chromium-rivertrail,markYoungH/chromium.src,rogerwang/chromium,ltilve/chromium,markYoungH/chromium.src,junmin-zhu/chromium-rivertrail,Fireblend/chromium-crosswalk,Just-D/chromium-1,bright-sparks/chromium-spacewalk,timopulkkinen/BubbleFish,rogerwang/chromium,patrickm/chromium.src,hgl888/chromium-crosswalk-efl,jaruba/chromium.src,hgl888/chromium-crosswalk,M4sse/chromium.src,anirudhSK/chromium,timopulkkinen/BubbleFish,zcbenz/cefode-chromium,krieger-od/nwjs_chromium.src,zcbenz/cefode-chromium,timopulkkinen/BubbleFish,mohamed--abdel-maksoud/chromium.src,bright-sparks/chromium-spacewalk,ChromiumWebApps/chromium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